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  • Author Author: tariq.ahmad
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Turning a Raspberry Pi Pico into a GPU! -- Episode-644

In this episode, Clem takes us through the intricacies of the Raspberry Pi Pico and graphics cards. Forget the technical jargon; imagine a graphics card as a translator between your CPU and the screen, a bit like those old-school graphics adapters but with a modern twist. Clem, our guide, dives into the world of microcontrollers, specifically the RP2040, cooking up digital concoctions for today's monitors and touchscreens. 

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Downloads & Links | Bill of Material | Discussion

But every journey has its bumps, and Clem hits a roadblock with high-speed video signals. Ever tried hand wiring on a breadboard? It can be a hit or a miss. Spoiler: It's a miss. Clem troubleshoots with DVI-Socks, dealing with impedance-matching intricacies using resistors. It's a bit like walking a tightrope – precision is key, but it's easy to slip. 

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The video navigates through connection experiments – soldering DVI sockets, trying headers – with Clem emphasizing the importance of stable connections over detachable boards. A nudge in the wrong direction, and the signal's out of sync. Clem wraps it up neatly with a PCB design, a more reliable solution for video signals with the Raspberry Pi Pico. 

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The plot thickens as Clem tackles the connection conundrum.  In the PCIe connector, Clem spots a hidden SMBus, an I2C bus in disguise.  This lets Clem attach the Pseudo-GPU to the SMBus via the PCI connector. 

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The grand finale showcases Clem's Arduino code, a practical display of text, colour, and rotation using the Adafruit GFX library. Clem demonstrates using two Raspberry Pi Pico boards, connected via I2C, showing them playing nicely with a small monitor. The graphics are very basic, but the concept opens doors for more creative projects. 

Downloads & Links:

Bonus Content Video:

Bill of Material:

Product Name Manufacturer Quantity Buy Kit
Raspberry pi pico Raspberry pi 2 Buy Now
 

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DVI Socket

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  • This is awesome. I had a similar thought on a MCU that was SPI bottlenecked to displays, and created a project I call Microgpu (github.com/.../microgpu). Right now it has an SDL and Esp32-S3 implementation, but everything's abstracted that it's expandable to a pi-pico and others as well. I have a Pi Pico with an HDMI port on it but I haven't had to the time to experiment with it yet (been focused on the esp32-S3 just due to higher RAM).

    I used a similar model you are, where you send it draw commands (draw triangle, draw rectangle, draw text) and the GPU then executes those commands on its own internal frame buffer. You can even pre-load textures onto it from the MCU, then do texture draws for sprite drawing. I use the latter to render some small MCU based games, and I've been able to achieve 100+ fps using this to render a 3d octehedron (MCU did the 3d math and determined where triangles go in screen space, then it instructs the GPU to draw them with a solid color based on lighting normals).

    I didn't think about making a PCIE board for it, that's pretty awesome.

  • in reply to KallDrexx

    that is aweseom!
    thanks for sharing your project!
    for time reasons I hvent implemented the drawing functions yet and focused only on text, but maybe it would make more sense to just port your project to a pico for the hdmi compatibility.

  • in reply to mayermakes

    Thanks.  Yeah I get the time thing.  I've only implemented a few fonts and a few basic drawing commands.  Last night I did get it working on those all-in-one esp32s3 + display boards that sell on Aliexpress for $14.  So the idea is you just buy those boards, flash the GPU firmware onto it, then wire it up to your MCU and go. 

    So for example there's this: https://www.youtube.com/watch?v=Wso_Nsh81CY.  That's a Meadow stm32 (running C#) using the accelerometer to do 3d math and compute the octohedren rotation.  Then passing the information to the 7" 800x480 all-in-one device for rendering.  I need to do some performance work and reduce memory back and forth, but it at least was pretty fast to spin that up as a proof of concept (previous uses use an ili9341 8-bit parallel display).

    Another example I got my UI example running on it too: https://www.youtube.com/watch?v=96u6pD-FAs8

    I just bought a FPGA and I may start learning FPGA work and maybe turning an FPGA into a GPU with that.  But that's a more long term idea :)

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  • in reply to mayermakes

    Thanks.  Yeah I get the time thing.  I've only implemented a few fonts and a few basic drawing commands.  Last night I did get it working on those all-in-one esp32s3 + display boards that sell on Aliexpress for $14.  So the idea is you just buy those boards, flash the GPU firmware onto it, then wire it up to your MCU and go. 

    So for example there's this: https://www.youtube.com/watch?v=Wso_Nsh81CY.  That's a Meadow stm32 (running C#) using the accelerometer to do 3d math and compute the octohedren rotation.  Then passing the information to the 7" 800x480 all-in-one device for rendering.  I need to do some performance work and reduce memory back and forth, but it at least was pretty fast to spin that up as a proof of concept (previous uses use an ili9341 8-bit parallel display).

    Another example I got my UI example running on it too: https://www.youtube.com/watch?v=96u6pD-FAs8

    I just bought a FPGA and I may start learning FPGA work and maybe turning an FPGA into a GPU with that.  But that's a more long term idea :)

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